India, Aug. 3 -- The BJP's defeat in the Bankipur Assembly bypoll, a constituency vacated by the party's national president Nitin Nabin and long regarded as one of its safest urban seats, has triggered unprecedented introspection within the party, with several leaders privately admitting that the result has exposed complacency, a failure to accurately assess voter sentiment and possible erosion in sections of the BJP's traditional support base.

Conversations by The Sunday Guardian with party leaders, MPs, MLAs and campaign functionaries after the results suggest that the scale and symbolism of the defeat have come as a major shock within the organisation. Several leaders said they had never imagined that the BJP could lose Bankipur, part...